Time-of-flight (TOF) cameras are based on a measurement of a delay between the emission of an optical infra-red (IR) signal, which is then reflected by an object, and the reception of the optical signal at a photon mixing device (PMD) imager. The measured delay is proportional to the distance of the object. This principle may be very sensitive to delays caused by the components inside the camera. For example, delays tend to occur between the electrical illumination-control signal generated by the chip and the actual emitted optical signal. For example, the driver of the illumination unit which emits the IR signal, may cause an additional (temperature and voltage dependent) delay, which may distort the measurement. Additionally, the driver consumes a lot of power and may disturb other sensitive building blocks on the chip. When the illumination unit is placed apart from the imager (e.g. in automotive applications the imager might be placed below the rear-view mirror and the illumination unit in the head lights) the control may be especially challenging and expensive due to long distances between the illumination unit and the imager.